Design, synthesis, and self-assembly behavior of C3-symmetry discotic molecules via click chemistry

Abstract

We prepared a series of C₃-symmetry discogens with three 1,2,3-triazoles and a central benzene ring by a copper-catalyzed “click reaction” between 1,3,5-triethynylbenzene and 3,4,5-trialkoxybenzyl azides. According to the differential scanning calorimetry (DSC) data, compounds with octyl and dodecyl peripheries showed stable liquid crystalline (LC) phases at room temperature, and upon heating underwent an isotropization at 105.3 °C and 92.2 °C, respectively. Compound with octadecyl peripheries melted into a LC phase at 63.5 °C, and changed into a disordered liquid at 84.4 °C. As characterized by optical polarized microscopy (POM) and X-ray scattering techniques, all LC phases revealed hexagonally packed columns, the axes of which are aligned vertically on the glass substrate. Interestingly, the experimentally accessible crystalline phase of the compound with octadecyl chains kept the 2-D hexagonal columnar structure, although the interdisc distance within the columns changed at the transition from the LC to crystalline phase.